Apparatus and methods for controlling gas pulsing in processes for depositing materials onto micro-device workpieces

ABSTRACT

An apparatus for depositing materials onto a micro-device workpiece includes a gas source system configured to provide a first precursor, a second precursor, and a purge gas. The apparatus can also include a valve assembly coupled to the gas source system. The valve assembly is configured to control a flow of the first precursor, a flow the second precursor, and a flow of the purge gas. Another component of the apparatus is a reaction chamber including an inlet coupled to the valve assembly, a workpiece holder in the reaction chamber, and an outlet downstream from the workpiece holder. The apparatus also includes a monitoring system and a controller. The monitoring system comprises a radiation source that directs a selected radiation through the reaction chamber and a detector that senses a parameter of the radiation directed through the reaction chamber. The controller is operatively coupled to the monitoring system and the valve assembly. The controller contains computer operable instructions to terminate the flow of the first precursor, the flow of the second precursor and/or the flow of the purge gas based on the parameter sensed by the monitoring system in real-time during a deposition cycle of a workpiece.

TECHNICAL FIELD

[0001] The present invention is related to apparatus and methods forcontrolling gas pulsing in thin film deposition processes used in themanufacturing of microdevices.

BACKGROUND

[0002] Thin film deposition techniques are widely used in themanufacturing of micro-devices to form a coating on a workpiece thatclosely conforms to the surface topography. The size of the individualcomponents in the devices is constantly decreasing, and the number oflayers in the devices is increasing. As a result, the density ofcomponents and the aspect ratios of depressions (e.g., the ratio of thedepth to the size of the opening) is increasing. The size of workpiecesis also increasing to provide more real estate for forming more dies(i.e., chips) on a single workpiece. Many fabricators, for example, aretransitioning from 200 mm to 300 mm workpieces, and even largerworkpieces will likely be used in the future. Thin film depositiontechniques accordingly strive to produce highly uniform conformal layersthat cover the sidewalls, bottoms and corners in deep depressions thathave very small openings.

[0003] One widely used thin film deposition technique is Chemical VaporDeposition (CVD). In a CVD system, one or more precursors that arecapable of reacting to form a solid thin film are mixed in a gas orvapor state, and then the precursor mixture is presented to the surfaceof the workpiece. The surface of the workpiece catalyzes the reactionbetween the precursors to form a thin solid film at the workpiecesurface. The most common way to catalyze the reaction at the surface ofthe workpiece is to heat the workpiece to a temperature that causes thereaction.

[0004] Although CVD techniques are useful in many applications, theyalso have several drawbacks. For example, if the precursors are nothighly reactive, then a high workpiece temperature is needed to achievea reasonable deposition rate. Such high temperatures are not typicallydesirable because heating the workpiece can be detrimental to thestructures and other materials that are already formed on the workpiece.Implanted or doped materials, for example, can migrate in the siliconsubstrate at higher temperatures. On the other hand, if more reactiveprecursors are used so that the workpiece temperature can be lower, thenreactions may occur prematurely in the gas phase before reaching thesubstrate. This is not desirable because the film quality and uniformitymay suffer, and also because it limits the types of precursors that canbe used. Thus, CVD techniques may not be appropriate for many thin filmapplications.

[0005] Atomic Layer Deposition (ALD) is another thin film depositiontechnique that addresses several of the drawbacks associated with CVDtechniques. FIGS. 1A and 1B schematically illustrate the basic operationof ALD processes. Referring to FIG. 1A, a layer of gas molecules A_(x)coats the surface of a workpiece W. The layer of A_(x) molecules isformed by exposing the workpiece W to a precursor gas containing A_(x)molecules, and then purging the chamber with a purge gas to removeexcess A_(x) molecules. This process can form a monolayer of A_(x)molecules on the surface of the workpiece W because the A_(x) moleculesat the surface are held in place during the purge cycle by physicaladsorption forces at moderate temperatures or chemisorption forces athigher temperatures. The layer of A_(x) molecules is then exposed toanother precursor gas containing B_(y) molecules. The A_(x) moleculesreact with the B_(y) molecules to form an extremely thin solid layer ofmaterial on the workpiece W. The chamber is then purged again with apurge gas to remove excess B_(y) molecules.

[0006]FIG. 2 illustrates the stages of one cycle for forming a thinsolid layer using ALD techniques. A typical cycle includes (a) exposingthe workpiece to the first precursor A_(x), (b) purging excess A_(x)molecules, (c) exposing the workpiece to the second precursor B_(y), andthen (d) purging excess B_(y) molecules. In actual processing severalcycles are repeated to build a thin film on a workpiece having thedesired thickness. For example, each cycle may form a layer having athickness of approximately 0.5-1.0 Å, and thus it takes approximately60-120 cycles to form a solid layer having a thickness of approximately60 Å.

[0007]FIG. 3 schematically illustrates an ALD reactor 10 having achamber 20 coupled to a gas supply 30 and a vacuum 40. The reactor 10also includes a heater 50 that supports the workpiece W and a gasdispenser 60 in the chamber 20. The gas dispenser 60 includes a plenum62 operatively coupled to the gas supply 30 and a distributor plate 70having a plurality of holes 72. In operation, the heater 50 heats theworkpiece W to a desired temperature, and the gas supply 30 selectivelyinjects the first precursor A_(x), the purge gas, and the secondprecursor B_(y) as shown above in FIG. 2. The vacuum 40 maintains anegative pressure in the chamber to draw the gases from the gasdispenser 60 across the workpiece W and then through an outlet of thechamber 20.

[0008] One drawback of ALD processing is that it has a relatively lowthroughput compared to CVD techniques. For example, ALD processingtypically takes about eight to eleven seconds to perform eachA_(x)-purge-B_(y)-purge cycle. This results in a total process time ofapproximately eight to eleven minutes to form a single thin layer ofonly 60 Å. In contrast to ALD processing, CVD techniques only requireabout one minute to form a 60 Å thick layer. The low throughput ofexisting ALD techniques limits the utility of the technology in itscurrent state because ALD may be a bottleneck in the overallmanufacturing process. Thus, it would be useful to increase thethroughput of ALD techniques so that they can be used in a wider rangeof applications.

[0009] Another drawback of ALD processing is that it is difficult tocontrol the uniformity of the deposited films over a long period oftime. One reason that it is difficult to consistently deposit uniformfilms is that the first precursor A_(x) and/or the second precursorB_(y) may ad sorb onto the surfaces of the reaction chamber 20. This maycause a build up of the first and second precursors that produces alayer of the deposited material on the components of the reactionchamber 20. Additionally, when the adsorption of the first precursorand/or the second precursor on the components of the reaction chamber 20reaches a saturation point, the precursors will then begin to desorpinto the gas flows in the reaction chamber 20. Such adsorption anddesorption of the precursors affects the quality of the layers ofmaterial deposited onto the workpieces. Therefore, there is also a needto provide better control of ALD processing to achieve more consistentresults throughout a run of workpieces.

SUMMARY

[0010] The present invention is directed toward reactors for depositingmaterials onto micro-device workpieces, systems that include suchreactors, and methods for depositing materials onto micro-deviceworkpieces. In one embodiment, an apparatus for depositing materialsonto a micro-device workpiece includes a gas source system configured toprovide a first precursor, a second precursor, and a purge gas. Theapparatus can also include a valve assembly coupled to the gas sourcesystem. The valve assembly is configured to control a flow of the firstprecursor, a flow the second precursor, and a flow of the purge gas.Another component of the apparatus is a reaction chamber including aninlet coupled to the valve assembly, a workpiece holder in the reactionchamber, and an outlet downstream from the workpiece holder. Theapparatus also includes a monitoring system and a controller. Themonitoring system comprises a radiation source that directs a selectedradiation through the gas flow and a detector that senses a parameter ofthe radiation. The controller is operatively coupled to the monitoringsystem and the valve assembly. The controller contains computer operableinstructions to terminate the flow of the first precursor, the flow ofthe second precursor and/or the flow of the purge gas based on theparameter sensed by the monitoring system in real-time during adeposition cycle of a workpiece.

[0011] The monitoring system can have several different embodiments. Inone embodiment, the monitoring system comprises a radiation source thatdirects the selected radiation through the reaction chamber between theinlet of the reaction chamber and the workpiece holder. In anotherembodiment, the monitoring system comprises a radiation source thatdirects the selected radiation through the reaction chamber downstreamfrom the workpiece holder. For example, the monitoring system caninclude a radiation source that directs radiation to a reflector withinthe reaction chamber that is immediately downstream from the workpiece,and the detector can be positioned to receive the radiation returningfrom the reflector. In another example, the radiation source can directthe radiation through the outlet flow, and the detector can bepositioned to receive the radiation passing through the outlet flow.

[0012] The monitoring system can be a spectroscope that measures theradiation absorbed by the first precursor, the second precursor, and/orthe purge gas. It will be appreciated that several different wavelengthsof radiation can be directed through the reaction chamber to determinethe concentration of each of the first precursor, the second precursorand the purge gas at different times throughout theA_(x)-purge-B_(y)-purge cycle. The monitoring system, therefore, cangenerally comprise a radiation source that directs a selected radiationthrough the reaction chamber and detector that senses a parameter of theradiation correlated to a quantity of the precursor and/or the purge gasin the reaction chamber.

[0013] The apparatus can be used to perform several methods fordepositing materials onto the micro-device workpieces. In oneembodiment, a method includes providing a flow of a first precursorthrough the reaction chamber to deposit the first precursor onto amicro-device workpiece, and subsequently providing a flow of a purge gasthrough the reaction chamber to purse excess amounts of the firstprecursor. This embodiment can further include monitoring a parametercorrelated to a quantity of the first precursor and/or the purge gas inthe reaction chamber as the first precursor and/or the purge gas flowthrough the reaction chamber. The flow of the first precursor and/or theflow of the purge gas is then terminated based upon the quantity of thefirst precursor and/or the purge gas in real-time. Different embodimentsof this method can be used to determine when a sufficient amount of oneof the precursors is in the reaction chamber to reach a desiredsaturation point. This is expected to provide a more accurate dosing ofthe precursors in the reaction chamber to compensate foradsorption/desorption of the precursors. Additional embodiments of thismethod include terminating the purge cycle according to the increasedlevel of the purge gas and/or the decreased level of the antecedentprecursor. This is expected to more accurately define the length of thepurge pulses in a manner that enhances the consistency of ALD processingand reduces the length of the purge pulses.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIGS. 1A and 1B are schematic cross-sectional views of stages inatomic layer deposition processing in accordance with the prior art.

[0015]FIG. 2 is a graph illustrating a cycle for forming a layer usingatomic layer deposition in accordance with the prior art.

[0016]FIG. 3 is a schematic representation of a system including areactor for vapor deposition of a material on to a microelectronicworkpiece in accordance with the prior art.

[0017]FIG. 4 is a schematic representation of a system having a reactorfor depositing a material onto a micro-device workpiece in accordancewith one embodiment of the invention.

[0018]FIG. 5 is a timing chart illustrating several aspects of methodsfor depositing materials onto micro-device workpieces in accordance withembodiments of the invention.

[0019]FIG. 6 is a schematic representation of a system having a reactorfor depositing material onto a micro-device workpiece in accordance withyet another embodiment of the invention.

[0020]FIG. 7 is a schematic representation of a system having a reactorfor depositing material onto a micro-device workpiece in accordance withstill another embodiment of the invention.

[0021]FIG. 8 is a schematic representation of a system having a reactorfor depositing material onto a micro-device workpiece in accordance withanother embodiment of the invention.

DETAILED DESCRIPTION

[0022] The following disclosure is directed toward reactors fordepositing a material onto a micro-device workpiece, systems includingsuch reactors, and methods for depositing a material onto a micro-deviceworkpiece. Many specific details of the invention are described belowwith reference to depositing materials onto micro-device workpieces. Theterm “micro-device workpiece” is used throughout to include substratesupon which and/or in which microelectronic devices, micromechanicaldevices, data storage elements, and other features are fabricated. Forexample, micro-device workpieces can be semi-conductor wafers, glasssubstrates, insulative substrates, or many other types of substrates.The term “gas” is used throughout to include any form of matter that hasno fixed shape and will conform in volume to the space available, whichspecifically includes vapors (i.e., a gas having a temperature less thanthe critical temperature so that it may be liquefied or solidified bycompression at a constant temperature). Additionally, several aspects ofthe invention are described with respect to Atomic Layer Deposition(“ALD”), but certain aspect may be applicable to other types ofdeposition processes. Several embodiments in accordance with theinvention are set forth in FIGS. 4-8 and the related text to provide athorough understanding of particular embodiments of the invention. Aperson skilled in the art will understand, however, that the inventionmay have additional embodiments, or that the invention may be practicedwithout several of the details in the embodiments shown in FIGS. 4-8.

[0023] A. Deposition Systems

[0024]FIG. 4 is a schematic representation of a system 100 fordepositing a material onto a micro-device workpiece W in accordance withan embodiment of the invention. In this embodiment, the system 100includes a reactor 110 having a reaction chamber 120 coupled to a gassupply 130 and a vacuum 140. For example, the reaction chamber 120 canhave an inlet 122 coupled to the gas supply 130 and an outlet 124coupled to the vacuum 140.

[0025] The gas supply 130 includes a plurality of gas sources 132(identified individually as 132 a-c), a valve assembly 133, and aplurality of gas lines 136 coupling the gas sources 132 to the valveassembly 133. The gas sources 132 can include a first gas source 132 afor providing a first precursor gas “A,” a second gas source 132 b forproviding a second precursor gas “B,” and a third gas source 132 c forproviding a purge gas “P.” The first and second precursors A and B canbe the constituents that react to form the thin, solid layer on theworkpiece W. The purge gas P can be a type of gas that is compatiblewith the reaction chamber 120 and the workpiece W. The valve assembly133 is coupled to a controller 142 that generates signals for pulsingthe individual gases through the reaction chamber 120 in a number ofcycles. Each cycle can include a first pulse of the first precursor A, asecond pulse of the purge gas P, a third pulse of the second precursorB, and a fourth pulse of the purge gas P. As explained in more detailbelow, several embodiments of the system 100 monitor and control thepulses of the first precursor A, the second precursor B, and/or thepurge gas P to provide consistent results and a high throughput.

[0026] The reactor 110 in the embodiment illustrated in FIG. 4 alsoincludes a workpiece support 150 and a gas distributor 160 in thereaction chamber 120. The workpiece support 150 can be a plate having aheating element to heat the workpiece W to a desired temperature forcatalyzing the reaction between the first precursor A and the secondprecursor B at the surface of the workpiece W. The workpiece support150, however, may not be heated in all applications. The gas distributor160 is coupled to the inlet 122 of the reaction chamber 120. The gasdistributor 160 has a compartment or plenum 162 and a distributor plate170. The distributor plate 170 has a plurality of passageways 172through which gasses flow into the reaction chamber 120 along a gas flowF.

[0027] B. Monitoring Systems

[0028] The system 100 shown in FIG. 4 also includes a monitoring systemthat monitors a parameter correlated to a quantity of the firstprecursor A, the second precursor B, and/or the purge gas P in the gasflow F. The monitoring system, for example, can determine theconcentration of the first precursor A, the second precursor B, and/orthe purge gas P at different times of the A_(x)-purge-B_(y)-purge pulsesin a cycle. The data generated by the monitoring system can be used tocontrol the pulse length of the first precursor A, the second precursorB, and/or the purge gas P to more consistently produce uniform layers onthe workpiece W or increase the throughput of workpieces through thereaction chamber 120.

[0029] One embodiment of a monitoring system for the system 100 includesa radiation source 182 that directs radiation through at least a portionof the gas flow F. As shown in FIG. 4, for example, the radiation source182 can direct a measurement beam 183 a through the reaction chamber 120at a location between the gas distributor 160 and the workpiece W. Theradiation source 182 can also direct a reference beam 183 b so that itis not affected by the gas flow F flowing through the reaction chamber120. It will be appreciated that not all of the embodiments of theradiation source 182 will require a reference beam 183 b. The monitoringsystem can also include a primary detector 184 that receives themeasurement beam 183 a and a reference detector 186 that receives thereference beam 183 b. The primary detector 184 generates a first signalcorresponding to a parameter of the measurement beam 183 a, such as theintensity of one or more wavelengths of radiation. Similarly, thereference detector 186 generates a second signal corresponding to theintensity or another parameter of the reference beam 183 b. The primarydetector 184 and the reference detector 186 are coupled to a comparator188 that compares the first signal from the primary detector 84 with thesecond signal from the reference detector 186. The comparator 188 thengenerates a measurement signal based upon the inputs from the primarydetector 184 and the reference detector 188.

[0030] The radiation source 182 and the primary detector 184 can beconfigured to monitor a particular wavelength of radiation that isaffected by the presence of a particular gas. For example, the radiationsource 182 can emit a radiation that is absorbed by one of the firstprecursor A, the second precursor B, or the purge gas P. In oneembodiment, the radiation source 182 emits a bandwidth of radiationhaving a spectrum of wavelengths and the primary detector 184 caninclude a filter that detects the presence of one or more wavelengthsthat are affected by the presence of the gases. The radiation source182, for example, can generate a sufficiently wide spectrum of radiationto include wavelengths that are affected by each of the first precursorA, the second precursor B, and the purge gas P; the primary detector 184can accordingly include separate filters that monitor the intensity ofthe individual wavelengths affected by each of the first precursor A,the second precursor B, and the purge gas P. In another embodiment, theradiation source 182 includes individual emitters that emit specificwavelengths or narrow bandwidths of radiation including a firstradiation having a first wavelength affected by the first precursor A,and second radiation having a second wavelength affected by the secondprecursor B, and a third radiation having a third wavelength affected bythe third precursor P. It will be appreciated that several other typesof radiation sources and detectors can be used. Suitable radiationsources and detectors are manufactured by INUSA or Online Technologies.

[0031] The monitoring system provides real-time data that is correlatedto the quantity of the particular constituents in the reaction chamber120. For example, as the individual gases flow in the gas flow F, theprimary detector 184 measures the change in intensity of the measurementbeam 183 a as it changes in correlation to the quantity of theindividual gases in the gas flow F. As explained above, the comparator188 uses the first signal from the primary detector 184 to generate ameasurement signal that provides an indication of the quantity of thefirst precursor A, the second precursor B, and/or the purge gas P in thereaction chamber or another portion of the gas flow F.

[0032] The controller 142 receives the signals from the comparator 188and sends control signals to the valve assembly 133. The control signalsfrom the controller 142 cause the valve assembly 133 to adjust the pulselength of the purge pulses and/or the precursor pulses. The controller142 accordingly contains computer operable instructions, such assoftware and/or hardware, that carry out embodiments of methods inaccordance with the invention for controlling the pulse width of thevarious gases. In general, the computer operable instructions adjust thepulse width of the purge pulses and/or the precursor pulses based on themeasurement signals correlated to the quantity of the first precursor A,the second precursor B, and/or the purge gas P in the gas flow F inreal-time during the deposition cycle of a workpiece W. The controller142 can accordingly adjust the pulse width for one or more the gasesduring the deposition cycle to compensate for variances in theprocessing of an individual workpiece and to increase the throughput ofan ALD process.

[0033] C. Deposition Methods

[0034]FIG. 5 is a timing diagram illustrating the individual flows ofthe first precursor A (labeled as Gas 1), the second precursor B(labeled as Gas 2), and the purge gas (labeled as Purge Gas) through thevalve assembly 133 (FIG. 4). The lower three lines show the on/offconfiguration of the valve assembly 133. FIG. 5 also shows the quantityof the individual gases in the reaction chamber or in the gas flow Fdownstream from the outlet. For example, the upper three lines show thepresence of the individual gases in the reaction chamber relative to theon/off cycling of the valve assembly 133.

[0035] The quantity of the precursors A and B fluctuates from zero to asaturation level throughout the cycles. Referring to FIG. 5, at time t₁the valve assembly 133 turns on the flow of the first precursor A shownby line 502. The quantity of the first precursor A increases for a ramptime t_(ramp1) until the quantity or concentration of the firstprecursor A reaches a desired saturation level. The flow of the firstprecursor A through the valve assembly 133 continues for a saturationperiod t_(sat1) until a time t₂. The period from t₁ to t₂ defines onepulse of the first precursor A. At time t₂, the valve assembly 133 turnsoff the flow of the first precursor A (line 502) and turns on the flowof the purge gas P (line 504). The presence of the first precursor Aaccordingly decreases (line 512) while the presence of the purge gas Paccordingly increases (line 514) until a time t₃ defining the endpointof the purge pulse. At time t₃, the valve assembly 133 turns off theflow of the purge gas P (line 504), and turns on the flow of the secondprecursor B (line 506). The presence of the purge gas P decreases (line514) while the presence of the second precursor B increases during aramp time t_(ramp2). The pulse of the second precursor B continues for asaturation time t_(sat2) until time t₄. The period from t₃ to t₄ definesone pulse of the second precursor B. At time t₄, the flow of the secondprecursor B is terminated (line 506) and the flow of the purge gas P isreinitiated (line 504) such that the presence of the second precursordecreases (line 516) while the presence of the purge gas P increases(line 514) between time t₄ and time t₅. The cycle of pulses from time t₁to t₅ is then repeated for as many cycles as are necessary to form alayer of material having a desired thickness.

[0036] One aspect of certain embodiments of methods in accordance withthe invention is controlling the duration of the precursor pulses for atleast one of the first precursor A or the second precursor B. Referringto FIGS. 4 and 5 together, the radiation source 182 and the primarydetector 184 can be configured to detect the concentration of the firstprecursor A. At time t₁ shown in FIG. 5, therefore, the comparator 188generates measurement signals corresponding to the increase in theconcentration of the first precursor A during the ramp time tramp. Whenthe measurement signal from the comparator 188 is at a predeterminedvalue corresponding to a desired concentration of the precursor A, orwhen the slope of the change in the measurement signal indicates thatthe ramp rate of the first precursor A is relatively low, then thecontroller 142 can set the duration of the pulse of the first precursorA to continue for an additional time period of t_(sat1). The time periodt_(sat1) can be a predetermined value that is programmed into thecontroller 142. The saturation period t_(sat1), for example, can bedetermined using empirical studies. It will be appreciated that the ramptime t_(ramp1) may vary throughout a run of workpieces because ofadsorption/desorption of the precursor in the reaction chamber 120. Thecontroller 142 can accordingly set the overall duration of the precursorpulse between time t₁ and t₂ to equal the measured ramp time t_(ramp1)plus the predetermined saturation time t_(sat1). A similar process canbe performed for controlling the duration of the pulse of the secondprecursor B between time t₃ and t₄ by configuring the radiation source182 and the primary detector 184 to measure the quantity of the secondprecursor B.

[0037] The system 100 can accordingly control the duration of theprecursor pulses in real-time during a processing cycle for a workpiece.This is expected to provide more uniform layers on workpieces because itinherently compensates for adsorption and desorption of the precursors.For example, if the precursors are adsorbing to the surfaces of thereaction chamber, the ramp time to bring the concentration of theprecursors to a desired level will increase because some molecules ofthe precursors will be extracted from the gas flow F before reaching theworkpiece W. The controller 142 compensates for adsorption of theprecursors by increasing the pulse width in real time according to themeasured ramp time. Conversely, if the precursors are desorping fromsurfaces of the reaction chamber 120, then the controller 142 willindicate a shorter ramp time and a corresponding shorter pulse width.Therefore, the system 100 and methods for controlling the duration ofthe precursor pulses are expected to provide real-time control ofindividual pulses of one or more of the precursors in a manner that isexpected to produce more uniform layers on the workpieces.

[0038] Another aspect of other embodiments of methods for depositing alayer of material onto a workpiece are directed toward controlling theduration of the purge pulses. In one embodiment, the radiation source182 and primary detector 184 are configured to detect the presence ofthe purge gas P. In this embodiment, the comparator 188 sendsmeasurement signals to the controller 142 corresponding to the increasein the purge gas P shown by line 514 of FIG. 5. When the purge gas Preaches a desired concentration and/or the slope of the increase of thepurge gas P is relatively low, then the controller 142 terminates thepurge cycle and begins a precursor cycle (e.g., at time t₃, t₅ and t₇).In another embodiment, the purge cycle is terminated by monitoring thepresence of one or more of the precursors. The controller 142 terminatesthe purge pulses when the presence of a precursor falls below a desiredlevel or the slope of the lines corresponding to the precursorconcentration (e.g., lines 512 and 516 in FIG. 5) is at a desired value.The pulse widths of the purge pulses can also be terminated using acombination of the presence of the precursor gas P and the firstprecursor A or second precursor B.

[0039] The controller 142 can accordingly adjust the length of the purgecycles to purge enough of the precursors from the reaction chamberwithout unnecessarily continuing the duration of the purge pulses. Thisis expected to provide better control over the deposition process in amanner that is likely to increase throughput and enhance the uniformityof the deposited layers. For example, conventional technology forsetting the endpoint of purge pulses involves determining a pulse widthusing empirical studies. This is typically accomplished in conventionalsystems by starting with long purge times, and then reducing the lengthof the purge times until an adequate amount of each of the precursors ispurged from the reaction chamber. This is a time consuming process, andit may not produce accurate results because of the adsorption anddesorption of the gases during a run of workpieces may change thenecessary duration of the purge pulses. The system 100 is expected toresolve these problems because the pulse width of the purge pulses arecontrolled in real-time to reduce the duration of the purge pulses in amanner that compensates for both adsorption and desorption during a runof workpieces. Therefore, several embodiments of methods for operatingthe system 100 are useful for enhancing the throughput of workpieces andthe uniformity of deposited layers.

[0040] D. Additional Embodiments of Deposition Systems

[0041] FIGS. 6-8 are schematic diagrams illustrating additionalembodiments of systems in accordance with the invention. Like referencenumbers refer to like components in FIGS. 4 and 6-8. FIG. 6 illustratesa system 600 in which the monitoring system includes a radiation source182 that directs a measurement beam 183 a through a gas flow F in theoutlet 124. The primary detector 184 can be positioned on another sideof the outlet 124. FIG. 7 illustrates a system 700 in which themonitoring system further includes a reflector 185 located justdownstream from the workpiece W. The reflector 185 can be a mirror oranother type of device that does not alter the measurement beam 183 aother than to change its direction. The reflector 185, for example, canbe mounted to the workpiece support 150. The radiation source 182 andthe primary detector 184 in the system 700 are configured to use thereflector 185 to direct the measurement beam 183 a from the radiationsource 182 to the primary detector 184. FIG. 8 illustrates a system 800in which the radiation source 182 is mounted to the workpiece holder 150in the reaction chamber 120. The radiation source 182 in the system 800directs the measurement beam 183 a to the primary detector 184. In thisembodiment, the monitoring system does not include a reference detector186 or a comparator 188. Instead, the detector 184 sends a measurementsignal directly to the controller 142. It will be appreciated that thecontroller 142 can include the hardware for receiving and processing themeasurement signal from the detector 184.

[0042] From the foregoing, it will be appreciated that specificembodiments of the invention have been described herein for purposes ofillustration, but that various modifications may be made withoutdeviating from the spirit and scope of the invention. For example,although the foregoing description describes several embodiments ashaving two precursors, it will be appreciated that the inventionincludes embodiments having more than two precursors. Additionally, itwill be appreciated that the same purge gas can be used betweenprecursor pulses, or that pulses of different purge gases can be usedfor purging different types of precursors. For example, an embodimentcan use a pulse of a first purge gas after a pulse of the firstprecursor and then a pulse of a second purge gas after a pulse of thesecond precursor; the first and second purge gases can be differentgases. Accordingly, the invention is not limited except as by theappended claims.

I/we claim:
 1. A method for depositing materials onto a micro-deviceworkpiece in a reaction chamber, comprising: providing a flow of a firstprecursor through the reaction chamber to deposit the first precursoronto a micro-device workpiece in the reaction chamber; providing a flowof a purge gas through the reaction chamber to purge excess amounts ofthe first precursor; monitoring a parameter correlated to a quantity ofthe first precursor and/or the purge gas in the reaction chamber as thefirst precursor and/or the purge gas flow through the reaction chamber;and terminating the flow of the first precursor and/or the flow of thepurge gas based on the monitored parameter of the quantity of the firstprecursor and/or the purge gas.
 2. The method of claim 1 whereinmonitoring a parameter correlated to a quantity of the first precursorand/or the purge gas comprises determining a concentration of the firstprecursor and/or the purge gas in the reaction chamber.
 3. The method ofclaim 1 wherein monitoring a parameter correlated to a quantity of thefirst precursor and/or the purge gas comprises determining aconcentration of the first precursor and/or the purge gas in thereaction chamber by directing a selected radiation through the reactionchamber and detecting a change in the radiation.
 4. The method of claim1 wherein monitoring a parameter correlated to a quantity of the firstprecursor and/or the purge gas comprises directing a selected radiationthrough the reaction chamber that is absorbed by the first precursor,detecting an intensity of the selected radiation, and indicating aquantity of the first precursor in the reaction chamber based on thedetected intensity of the selected radiation.
 5. The method of claim 1wherein monitoring a parameter correlated to a quantity of the firstprecursor and/or the purge gas in the reaction chamber comprisesdirecting a selected radiation through the reaction chamber that isabsorbed by the purge gas, detecting an intensity of the selectedradiation, and indicating a quantity of the purge gas in the reactionchamber based on the detected intensity of the selected radiation. 6.The method of claim 1 wherein: providing a flow of the first precursorcomprises injecting a pulse of the first precursor into the reactionchamber; monitoring a parameter correlated to a quantity of the firstprecursor and/or the purge gas comprises determining a concentration ofthe first precursor in the reaction chamber during the pulse of thefirst precursor and detecting when the concentration of the firstprecursor increases to a desired level; and the method further comprisesterminating the pulse of the first precursor at a predetermined periodof time after the concentration of the first precursor reaches thedesired level.
 7. The method of claim 1 wherein: providing a flow of thepurge gas comprises injecting a pulse of the purge gas into the reactionchamber; monitoring a parameter correlated to a quantity of the firstprecursor and/or the purge gas comprises determining a concentration ofthe first precursor in the reaction chamber during the pulse of thepurge gas; and the method further comprises terminating the pulse of thepurge gas when the concentration of the first precursor decreases to anacceptable level for introducing a second precursor into the reactionchamber.
 8. The method of claim 1 wherein: providing a flow of the purgegas comprises injecting a pulse of the purge gas into the reactionchamber; monitoring a parameter correlated to a quantity of the firstprecursor and/or the purge gas comprises determining a concentration ofthe purge gas in the reaction chamber during the pulse of the purge gas;and the method further comprises terminating the pulse of the purge gaswhen the concentration of the purge gas increases to an acceptable levelfor introducing a second precursor into the reaction chamber.
 9. Themethod of claim 1 wherein monitoring a parameter correlated to aquantity of the first precursor and/or the purge gas comprisesdetermining a concentration of the first precursor and/or the purge gasby directing a selected radiation through the flow of the firstprecursor and/or the flow of the purge gas upstream relative to theworkpiece.
 10. The method of claim 1 wherein monitoring a parametercorrelated to a quantity of the first precursor and/or the purge gascomprises determining a concentration of the first precursor and/or thepurge gas by directing a selected radiation through the flow of thefirst precursor and/or the flow of the purge gas downstream relative tothe workpiece.
 11. A method for depositing materials onto a micro-deviceworkpiece in a reaction chamber, comprising: providing a flow of a firstprecursor through the reaction chamber to deposit the first precursoronto a micro-device workpiece; providing a flow of a purge gas throughthe reaction chamber to purge excess amounts of the first precursor;determining a concentration of the first precursor and/or the purge gasin the reaction chamber as the first precursor and/or the purge gas flowthrough the reaction chamber; and terminating the flow of the firstprecursor and/or the flow of the purge gas based on the determinedconcentration of the first precursor or the purge gas.
 12. The method ofclaim 11 wherein determining a concentration of the first precursorand/or the purge gas comprises directing a selected radiation throughthe reaction chamber and detecting a change in the radiation.
 13. Themethod of claim 11 wherein determining a concentration of the firstprecursor and/or the purge gas comprises directing a selected radiationthrough the reaction chamber that is absorbed by the first precursor,detecting an intensity of the selected radiation, and indicating aquantity of the first precursor in the reaction chamber based on thedetected intensity of the selected radiation.
 14. The method of claim 11wherein determining a concentration of the first precursor and/or thepurge gas comprises directing a selected radiation through the reactionchamber that is absorbed by the purge gas, detecting an intensity of theselected radiation, and indicating a quantity of the purge gas in thereaction chamber based on the detected intensity of the selectedradiation.
 15. The method of claim 11 wherein: providing a flow of thefirst precursor comprises injecting a pulse of the first precursor intothe reaction chamber; determining a concentration of the first precursorand/or the purge gas comprises determining a concentration of the firstprecursor in the reaction chamber during the pulse of the firstprecursor and detecting when the concentration of the first precursorincreases to a desired level; and the method further comprisesterminating the pulse of the first precursor at a predetermined periodof time after the concentration of the first precursor reaches thedesired level.
 16. The method of claim 11 wherein: providing a flow ofthe purge gas comprises injecting a pulse of the purge gas into thereaction chamber; determining a concentration of the first precursorand/or the purge gas comprises determining a concentration of the firstprecursor in the reaction chamber during the pulse of the purge gas; andthe method further comprises terminating the pulse of the purge gas whenthe concentration of the first precursor decreases to an acceptablelevel for introducing a second precursor into the reaction chamber. 17.The method of claim 11 wherein: providing a flow of the purge gascomprises injecting a pulse of the purge gas into the reaction chamber;determining a concentration of the first precursor and/or the purge gascomprises determining a concentration of the purge gas in the reactionchamber during the pulse of the purge gas; and the method furthercomprises terminating the pulse of the purge gas when the concentrationof the purge gas increases to an acceptable level for introducing asecond precursor into the reaction chamber.
 18. A method for depositingmaterials onto a micro-device workpiece in a reaction chamber,comprising: providing a flow of a first precursor through the reactionchamber to deposit the first precursor onto a micro-device workpiece;monitoring a parameter related to the quantity of the first precursor inthe reaction chamber during the flow of the first precursor to determinewhen the quantity of the first precursor has reached a desired level;terminating the flow of the first precursor at a predetermined period oftime after the quantity of the first precursor reaches the desiredlevel; and providing a flow of a purge gas through the reaction chamberto purge excess amounts of the first precursor.
 19. The method of claim18 wherein monitoring a parameter related to the quantity of the firstprecursor comprises determining a concentration of the first precursorin the reaction chamber.
 20. The method of claim 18 wherein monitoring aparameter related to the quantity of the first precursor comprisesdirecting a radiation having a wavelength absorbed by the firstprecursor through the reaction chamber and detecting a change inintensity of the radiation.
 21. The method of claim 18, furthercomprising generating a signal that the quantity of the first precursorhas reached the desired level when the monitored parameter has increasedto a predetermined value corresponding to an end of a ramp time of apulse of the first precursor.
 22. The method of claim 18, furthercomprising generating a signal that the quantity of the first precursorhas reached the desired level when a slope of a change in the monitoredparameter is at a value corresponding to an end of a ramp time of apulse of the first precursor.
 23. A method for depositing materials ontoa micro-device workpiece in a reaction chamber, comprising: providing aflow of a first precursor through the reaction chamber to deposit thefirst precursor onto a micro-device workpiece; determining aconcentration of the first precursor in the reaction chamber as thefirst precursor flows through the reaction chamber by detecting a changein a radiation energy directed through the reaction chamber; terminatingthe flow of the first precursor at a predetermined period of time afterthe detected change in the radiation energy corresponds to a desiredconcentration of the first precursor in the reaction chamber; andproviding a flow of a purge gas through the reaction chamber to purgeexcess amounts of the first precursor.
 24. The method of claim 23wherein determining a concentration of the first precursor comprisesdirecting a radiation having a wavelength absorbed by the firstprecursor through the reaction chamber and detecting a change inintensity of the wavelength absorbed by the first precursor.
 25. Themethod of claim 23, further comprising generating a signal that thequantity of the first precursor has reached the desired level when theconcentration of the first precursor has increased to a predeterminedvalue corresponding to an end of a ramp time of a pulse of the firstprecursor.
 26. The method of claim 23, further comprising generating asignal that the quantity of the first precursor has reached the desiredlevel when a slope of a change in the concentration of the firstprecursor is at a value corresponding to an end of a ramp time of apulse of the first precursor.
 27. A method for depositing materials ontoa micro-device workpiece in a reaction chamber, comprising: providing aflow of a first precursor through the reaction chamber to deposit thefirst precursor onto a micro-device workpiece; providing a flow of apurge gas through the reaction chamber to purge excess amounts of thefirst precursor; monitoring a parameter related to a quantity of thefirst precursor and/or the purge gas in the reaction chamber as thepurge gas flows through the reaction chamber to determine when a desiredamount of the first precursor has been purged from the reaction chamber;and terminating the flow of the purge gas after determining when adesired amount of the first precursor has been removed from the reactionchamber.
 28. The method of claim 27 wherein monitoring a parameterrelated to the quantity of the purge gas and/or the first precursorcomprises determining a concentration of the first precursor in thereaction chamber.
 29. The method of claim 27 wherein monitoring aparameter related to the quantity of the purge gas and/or the firstprecursor comprises directing a radiation having a wavelength absorbedby the first precursor through the reaction chamber and detecting achange in intensity of the radiation.
 30. The method of claim 27 whereinmonitoring a parameter related to the quantity of the purge gas and/orthe first precursor comprises determining a concentration of the purgegas in the reaction chamber.
 31. The method of claim 27 whereinmonitoring a parameter related to the quantity of the purge gas and/orthe first precursor comprises directing a radiation having a wavelengthabsorbed by the purge gas through the reaction chamber and detecting achange in intensity of the radiation.
 32. The method of claim 27,further comprising generating a signal that the first precursor has beenpurged when a concentration of the first precursor has decreased to apredetermined value corresponding to an end of a purge gas pulse. 33.The method of claim 27, further comprising generating a signal that thefirst precursor has been purged when a concentration of the purge gashas increased to a predetermined value corresponding to an end of apurge gas pulse.
 34. A method for depositing materials onto amicro-device workpiece in a reaction chamber comprising. providing aflow of a first precursor through the reaction chamber to deposit thefirst precursor onto a micro-device workpiece; providing a flow of apurge gas through the reaction chamber to purge excess amounts of thefirst precursor; determining a concentration of the first precursorand/or the purge gas in the reaction chamber as the purge gas flowsthrough the reaction chamber by detecting a change in a radiation energydirected through the reaction chamber; and terminating the flow of thepurge gas when the detected change in the radiation energy correspondsto a desired concentration of the first precursor and/or the purge gasin the reaction chamber.
 35. The method of claim 34 wherein determininga concentration of the purge gas and/or the first precursor comprisesdirecting a radiation having a wavelength absorbed by the firstprecursor through the reaction chamber and detecting a change inintensity of the wavelength absorbed by the first precursor.
 36. Themethod of claim 34 wherein determining a concentration of the purge gasand/or the first precursor comprises directing a radiation having awavelength absorbed by the purge gas through the reaction chamber anddetecting a change in intensity of the wavelength absorbed by the purgegas.
 37. A method for depositing materials onto a micro-device workpiecein a reaction chamber, comprising: providing a flow of a first precursorthrough the reaction chamber to deposit the first precursor onto amicro-device workpiece; monitoring a parameter related to the quantityof the first precursor in the reaction chamber as the first precursorflows through the reaction chamber to determine when the quantity of thefirst precursor has reached a desired level; terminating the flow of thefirst precursor at a predetermined period of time after the quantity ofthe first precursor reaches the desired level; providing a flow of apurge gas through the reaction chamber to purge excess amounts of thefirst precursor; monitoring a parameter related to a quantity of thefirst precursor and/or the purge gas in the reaction chamber as thepurge gas flows through the reaction chamber to determine when a desiredamount of the first precursor has been purged from the reaction chamber;and terminating the flow of the purge gas after determining when adesired amount of the first precursor has been removed from the reactionchamber.
 38. A method for depositing materials onto a micro-deviceworkpiece in a reaction chamber, comprising: providing a flow of a firstprecursor through the reaction chamber to deposit the first precursoronto a micro-device workpiece; determining a concentration of the firstprecursor in the reaction chamber as the first precursor flows throughthe reaction chamber by detecting a change in a radiation energydirected through the reaction chamber; terminating the flow of the firstprecursor at a predetermined period of time after the detected change inthe radiation energy corresponds to a desired concentration of the firstprecursor in the reaction chamber; providing a flow of a purge gasthrough the reaction chamber to purge excess amounts of the firstprecursor; determining a concentration of the first precursor and/or thepurge gas in the reaction chamber as the purge gas flows through thereaction chamber by detecting a change in a radiation energy directedthrough the reaction chamber; and terminating the flow of the purge gaswhen the detected change in the radiation energy corresponds to adesired concentration of the first precursor and/or the purge gas in thereaction chamber.
 39. An apparatus for depositing materials onto amicro-device workpiece in a reaction chamber, comprising: a gas sourcesystem configured to provide a first precursor, a second precursor, anda purge gas; a valve assembly coupled to the gas source system, thevalve assembly being configured to control a flow of the firstprecursor, a flow of the second precursor, and a flow of the purge gas;a reaction chamber including an inlet coupled to the valve assembly, aworkpiece holder, and an outlet; a monitoring system comprising aradiation source that directs a selected radiation through the flow ofthe first precursor, the flow of the second precursor and/or the flow ofthe purge gas, and a detector that senses a parameter of the selectedradiation; and a controller operatively coupled to the monitoring systemand the valve assembly, the controller containing computer operableinstructions to terminate the flow of the first precursor, the flow ofthe second precursor and/or the flow of the purge gas based on theparameter sensed by the monitoring system in real-time during adeposition cycle of a workpiece.
 40. The apparatus of claim 39 whereinthe radiation source is configured to direct a measurement beam ofradiation through the reaction chamber between the inlet and theworkpiece holder.
 41. The apparatus of claim 39 wherein the radiationsource is configured to direct a measurement beam of radiation through aportion of a gas flow after the gas flow passes by a workpiece on theworkpiece holder.
 42. The apparatus of claim 39 wherein: the monitoringsystem further comprises a reflector in the reaction chamber; theradiation source is configured to direct a measurement beam of radiationto the reflector; and the detector is configured to receive a portion ofthe radiation beam returning from the reflector.
 43. The apparatus ofclaim 39 wherein the radiation source and the detector are configured tomeasure a change in intensity of a wavelength of radiation absorbed bythe first precursor.
 44. The apparatus of claim 39 wherein the radiationsource and the detector are configured to measure a change in intensityof a wavelength of radiation absorbed by the purge gas.
 45. Theapparatus of claim 39 wherein the radiation source and the detector areconfigured to measure a change in intensity of a first wavelength ofradiation absorbed by the first precursor and a change in intensity of asecond wavelength of radiation absorbed by the purge gas.
 46. Anapparatus for depositing materials onto a micro-device workpiece in areaction chamber, comprising: a gas source system; a valve assemblycoupled to the gas source system, the valve assembly being configured tocontrol a flow of a precursor and a flow of a purge gas; a reactionchamber including an inlet coupled to the valve assembly, a workpieceholder, and an outlet; and a monitoring system that senses a parametercorrelated to a quantity of the precursor and/or the purge gas in thereaction chamber.
 47. The apparatus of claim 46 wherein the monitoringsystem further comprises a radiation source configured to direct aselected radiation through the reaction chamber and a detector thatsenses a change in the radiation correlated to a concentration of theprecursor and/or the purge gas in the reaction chamber.
 48. Theapparatus of claim 47 wherein the radiation source is configured todirect a measurement beam of radiation through the reaction chamberbetween the inlet and the workpiece holder.
 49. The apparatus of claim47 wherein the radiation source is configured to direct a measurementbeam of radiation through a portion of a gas flow after the gas flowpasses by a workpiece on the workpiece holder.
 50. The apparatus ofclaim 47 wherein: the monitoring system further comprises a reflector inthe reaction chamber; the radiation source is configured to direct ameasurement beam of radiation to the reflector; and the detector isconfigured to receive a portion of the radiation beam returning from thereflector.
 51. The apparatus of claim 47 wherein the radiation sourceand the detector are configured to measure a change in intensity of awavelength of radiation absorbed by the first precursor.
 52. Theapparatus of claim 47 wherein the radiation source and the detector areconfigured to measure a change in intensity of a wavelength of radiationabsorbed by the purge gas.
 53. The apparatus of claim 47 wherein theradiation source and the detector are configured to measure a change inintensity of a first wavelength of radiation absorbed by the firstprecursor and a change in intensity of a second wavelength of radiationabsorbed by the purge gas.
 54. An apparatus for depositing materialsonto a micro-device workpiece in a reaction chamber, comprising: a gassource system configured to provide a first precursor, a secondprecursor, and a purge gas; a valve assembly coupled to the gas sourcesystem, the valve assembly being configured to control a flow of thefirst precursor, a flow of the second precursor and a flow of the purgegas; a reaction chamber including a gas distributor, a workpiece holderjuxtaposed to the gas distributor, and an outlet; a monitoring systemcomprising a radiation source and a detector, wherein the radiationsource directs a selected radiation through the reaction chamber betweenthe gas distributor and the workpiece holder, and wherein the detectorsenses a parameter of the radiation directed through the reactionchamber that is correlated to a quantity of the first precursor, thesecond precursor and/or the purge gas; and a controller operativelycoupled to the monitoring system and the valve assembly, the controllercontaining computer operable instructions to terminate the flow of thefirst precursor, the flow of the second precursor and/or the flow of thepurge gas based on the parameter sensed by the monitoring system inreal-time during a deposition cycle of a workpiece.
 55. An apparatus fordepositing materials onto a micro-device workpiece in a reactionchamber, comprising: a gas source system configured to provide a firstprecursor, a second precursor, and a purge gas; a valve assembly coupledto the gas source system, the valve assembly being configured to controla flow of the first precursor, a flow of the second precursor and a flowof the purge gas; a reaction chamber including a gas distributor, aworkpiece holder juxtaposed to the gas distributor, and an outlet; amonitoring system comprising a radiation source and a detector, whereinthe radiation source directs a selected radiation through a portion ofthe gas flow passes by a workpiece location of the workpiece holder, andwherein the detector senses a parameter of the radiation directedthrough the reaction chamber; and a controller operatively coupled tothe monitoring system and the valve assembly, the controller containingcomputer operable instructions to terminate the flow of the firstprecursor, the flow of the second precursor and/or the flow of the purgegas based on the parameter sensed by the monitoring system in real-timeduring a deposition cycle of a workpiece.
 56. An apparatus fordepositing materials onto a micro-device workpiece in a reactionchamber, comprising: a gas source system configured to provide a firstprecursor, a second precursor, and a purge gas; a valve assembly coupledto the gas source system, the valve assembly being configured to controla flow the first precursor, a flow of the second precursor and a flow ofthe purge gas; a reaction chamber including an inlet coupled to thevalve assembly, a workpiece holder, and an outlet; a monitoring systemconfigured to determine a parameter correlated to a quantity of thefirst precursor, the second precursor and/or the purge gas as the firstprecursor, the second precursor and/or the purge gas flows through thereaction chamber; and a controller operatively coupled to the monitoringsystem and the valve assembly, the controller containing computeroperable instructions to terminate the flow of the first precursor, theflow of the second precursor and/or the flow of the purge gas based onthe parameter determined by the monitoring system.
 57. An apparatus fordepositing materials onto a micro-device workpiece in a reactionchamber, comprising: a gas source system configured to provide a firstprecursor, a second precursor, and a purge gas; a valve assembly coupledto the gas source system, the valve assembly being configured to controla flow the first precursor, a flow of the second precursor and a flow ofthe purge gas; a reaction chamber including an inlet coupled to thevalve assembly, a workpiece holder, and an outlet; a monitoring systemconfigured to determine a concentration of the first precursor, thesecond precursor and/or the purge gas as the first precursor, the secondprecursor and/or the purge gas flows through the reaction chamber; and acontroller operatively coupled to the monitoring system and the valveassembly, the controller containing computer operable instructions toterminate the flow of the first precursor, the flow of the secondprecursor and/or the flow of the purge gas based on the concentrationdetermined by the monitoring system.